The present invention relates to an apparatus and method for radio reception equipped with an adaptive array antenna capable of controlling directivity.
An adaptive array antenna is known as an antenna system that can control directivity. xe2x80x9cWaveform Equalization Technology for Digital Mobile Communicationsxe2x80x9d (compiled under the supervision of Jun Horikoshi, Triceps Co., Ltd.) describes that in an array antenna consisting of a plurality of antennas, applying an amplitude/phase shift to the output of each antenna and then combining them will change the directivity of the array. The adaptive array antenna uses the principle above, and adaptively controls directivity in accordance with changes in surrounding conditions by determining a weighting factor of each antenna output based on a certain control algorithm and multiplying each antenna output by this weighting factor.
FIG. 1 is a block diagram showing a configuration of a conventional adaptive array antenna apparatus (hereinafter referred to as xe2x80x9creception adaptive arrayxe2x80x9d). As shown in the figure, antenna outputs 2 of a plurality of antennas 1 are multiplied by weighting factors 3 respectively and the antenna outputs weighted with these weighting factors 3 for respective antennas are combined into array output 4.
Weighting factors for their respective antenna outputs are controlled by weighting factor control section 5. Weighting factor control section 5 uses three kinds of information to control weighting factors; array combined output 4, respective antenna outputs 2 and advance knowledge 6 regarding a desired signal. There is also a system that does not use array output 4 to control weighting factors.
Conventionally, a weighting factor control algorithm assuming synchronous interference is applied to weighting factor control section 5. In a weighting factor control algorithm assuming synchronous interference, weighting factors are controlled so as to eliminate such an interference signal that is present continuously during the interval from the beginning to the end of a desired signal (hereinafter referred to as xe2x80x9csynchronous interferencexe2x80x9d) as shown in FIG. 2.
However, if a signal provided by a communication user who is different from the communication user who is transmitting the desired signal is the interference signal, synchronization between the desired signal and interference signal is not guaranteed, and there is a possibility that the interference signal will mix into the desired signal at some midpoint as shown in FIG. 3.
Thus, the conventional system has the problem that, if the interference signal mixes into the desired signal at some midpoint, the weighting factors calculated using a known signal of the desired signal before the interference signal starts to interfere cannot fully eliminate the interference signal.
It is an objective of the present invention to provide an apparatus and method for adaptive array antenna radio reception that can appropriately control weighting factors for array combination and effectively eliminate or suppress an interference signal even if the interference signal mixes into a desired signal at some midpoint.
This objective is achieved by a radio reception apparatus comprising a combination section that weights and then combines reception signals corresponding to a plurality of antenna elements respectively and a factor adaptation section that adaptively controls weighting of the reception signals above according to the time at which the interference signal mixes into the desired signal.